Abstract:

Objective   To investigate expression of immunoglobulin-like transcript 2(ILT2) and its relationship with biological behavior and clinicopathoiogical features in gastric carcinoma tissues and cell lines. Methods   Expression of the ILT2 protein was detected by the immunohistochemical SP method in 50 cases of gastric tissues. Correlations of expression of the ILT2 protein with clinicopathoiogical features were analyzed. Protein and mRNA expressions of ILT2 in 6 gastric cancer cell lines with diverse differentiation (highly differentiated, MKN1; moderately differentiated, SGC-7901 and AGS; lowly differentiated, MGC-803; undifferentiated, HGC-27 and BCG-823) were analyzed by Real-time fluorescent quantitative PCR and FACS flow cytometry. Cytolytic activities of freshly isolated PBMC cells and NK-92 cells against MKN1 and HGC-27 were determined by MTT assay. Results   Expression of ILT2 was higher in gastric cancer tissues(31/50, 62.0%), while there was no ILT2 expression in normal gastric tissues. Expression of ILT2 was significantly higher in poorly differentiated cancer tissues(22/30, 73.3%) than in well-differentiated tissues(9/20, 45%)(χ2=4.089，P<0.05). Also, expression of ILT2 was significantly higher in bigger tumor size with D>5cm (16/19, 84.2%) than in smaller tumor size with D<5cm(15/31, 48.4%）(χ2=6.417，P<0.01). ILT2 mRNA and protein were differently expressed in all the 6 gastric cancer cell lines, and lowly differentiated and undifferentiated gastric cancer cell lines had higher ILT2 expression than moderately and highly differentiated cell lines(P<0.05). Cytolytic activities of PBMC and NK-92 cells against ILT2high HGC-27 cells were lower than those against ILT2low MKN1 cells in different effector-target ratios (P<0.05). Conclusion   The inhibitory receptor ILT2 is expressed in gastric carcinoma and its expression level is related to differentiation stage and clinicopathoiogical features. PBMCs and NK-92 cells show lower cytolytic activity against ILT2high gastric cancer cells. ILT2 may be involved in tumor escape and is expected to become a new target to diagnose and treat gastric cancer.

Key words: Immunoglobulin-like transcript 2; Gastric neoplasms; Natural killer cells